Several types of electronic circuits employ a power transformer circuit for providing voltage gain, impedance matching, and current limiting. Power transformer circuits usually require an inductive element that is typically realized using a conventional magnetic inductor.
Conventional magnetic inductors are physically large, heavy devices that are both costly to construct and difficult to automate. Magnetic inductors are also among the most ill-behaved of electrical components with regard to parameter tolerances and nonlinear effects, the latter being particularly troublesome in high frequency applications. Due to winding resistance and core characteristics, magnetic inductors dissipate significant amounts of electrical power in the form of heat. The heat produced by magnetic inductors not only detracts from circuit energy efficiency, but also requires that other circuit components be selected with high temperature ratings in order to maintain circuit reliability.
Further, because of these dissipative factors, magnetic inductors have a relatively low "quality factor" (i.e., "Q"), Accordingly, power transformer circuits that employ magnetic inductors have limited voltage gain capabilities. As a consequence of these shortcomings of magnetic inductors, the resulting power transformer circuit tends to be physically large and costly, prone to nonlinear effects and considerable variations in key parameters, constrained in voltage gain capability, and significantly sub-optimal with regard to energy efficiency and reliability.
In recent years, a number of efforts have been made to apply certain electromechanical devices, such as piezoelectric transformers (e.g., Rosen bar transformers), to power supplies and other types of energy transfer circuits. While it has been realized that these devices are, under certain modes of operation, considerably more energy efficient and capable of providing higher voltage gain than conventional magnetic inductors, most efforts have been limited to low power circuits for transferring relatively small amounts of power. Further, most existing approaches require considerable complexity in the physical structure of the devices themselves and/or additional control circuitry in order to operate the devices in an efficient manner.
It is therefore apparent that a need exists for a power transformer circuit that provides efficient transfer of a considerable amount of electrical power, that is smaller in size, lighter in weight, and less thermally dissipative than circuits using ordinary magnetic inductors, that provides high voltage gain, that employs devices with relatively simple physical structures, and that does not require complicated control circuitry. Such a power transformer circuit would represent a considerable advance over the prior art.